so i bought this in march and this is what i have learned about 351m motors

1. the oiling problems these are known for is a myth..

This myth is one that most everyone, even people who like the "M" engines, hold as being fact. Some people believe that because the "M" engines have a larger journal diameter than the Cleveland engines that Ford "forgot" to restrict the oiling galleries to make up for it. Well, if this is so then why isn't the 351W rumored to have the same problems due to fact that it has the same journal diameter as the "M" engines?, Also, installing a 400 crank shaft in a 351W has become a popular "stroker kit" for this engine, yet no one is complaining about 400 CID Windsor engines throwing crank shafts! And what about all of the "M" engines out there with 200 or even 300K miles on them without a rebuild? Despite all this, some people still insist that there are abnormal oiling problems with this engine. There is even an "oiling restrictor kit" available from Moroso to supposedly "fix" this "problem". This kit is designed for high-volume oil pumps in racing applications only. From my experience the only time an "M" block may experience oiling problems on the crankshaft is if someone installed a full-competition high-volume oil pump in an engine driven on the street. I used a standard volume Melling oil pump on my engine and it has fantastic oil pressure! The only thing I can think of that may have "fueled the fire" on the "M" oiling problem rumor is the fact that this engine was installed mostly in full-size 4x4 trucks and even saw duty in many 1-ton F-350s. Many of these trucks were used to tow enormous amounts of weight back in the days before overdrive transmissions. The "M" engines were also some of the first small block engines that were now being asked to do the job previously reserved only for super heavy-duty big block engines. It is quite possible that some "M" motors may have worn out sooner than some of the older HD big block truck engines. However, I believe that the "M" engines are the only small blocks made by anyone that can even attempt to take this kind of abuse. I think the "M" engines simply got a bad rap because they were being used in applications where no small block engine should have been in the first place. In short, if you need to tow a 10,000+ pound trailer on a daily basis, then get a diesel or a HD rated gas engine. But if you use the "M" small blocks they way they were intended to be used (i.e. in a half-ton Bronco) and you don't exceed your Bronco's rated towing capacity, then you should get many, many miles of trouble-free service out of it.

2. there is no way to build up an "M" motor.... Actually, this is not entirely true. Ford build plenty of HI-PO 351 Cleveland's, which is very similar to the "M" block engines. The main difference between the 351C and 351M/400 are the length of the connecting rods, which are 0.8" longer on the "M" engines, the main journal size, which is 2.75" on the 351C and 3.0" on the "M" engines, the block deck height which is 1.09" taller than the 351C, the intake manifold which is about 1" wider than the 351C, and the transmission bolt pattern. The cylinder heads, the distributors, the entire valve train (except for the push rods), the water pumps, the oil pans, the fuel pumps, and the oil pumps will interchange between the 351C and the "M" engines. Therefore, there are plenty of HI-PO parts that were designed for the 351C that will work on the "M" engines. Besides, who in the world actually has factory original HI-PO parts from engines such as the Boss 302 and the 429 SCJ on their 302 or 460 truck engines? Folks, this is what the a-f-t-e-r-m-a-r-k-e-t parts industry is for!

3.the "M" block is heavier than the 429/460 block. huh? where did that come from? it is approx 150lbs lighter

4.they are only good for boat anchors.... i don't know if you ever tried to pull up a 550lb anchor before but it sucks!

anyway i also have found a company that makes a blower for the 400M and am waiting for a response as to weather or not it will fit the 351M...

also the beast now has a 10000lb warn winch, 33/13.5/15 boggers mounted on 12.5x15 prime 5 stars, 3 kc's on a light bar i made from a weather guard ladder rack (got tired of waiting for fedex to deliver the one i bought so i made my own) i have 4v "C" heads on the way and a torkerII intake, and an edelbrock 600 carb comming...

 

You need the Edelbrock heads for the M. They are better then the cleaveland, and way easier to get ahold of then the Austrailian closed chamber 2V heads.

M's like the Cleavelands do have an oiling issue, but is not that big of deal. It has something to do with priority oiling in heavy track conditions. There is a good external feed tube that I have seen in the past, but I don't know if someone got around this by now. Moroso restrictors are for solid cammed motors not hydraulics since they require less oil to pump up.

The problem with the M's is the weight, and serious lack of any good heads. The open chamber heads they had were crap, and would detonate with out proper care past 9-1. They are none the less a rock solid foundation, but they do need good heads and that is now fixed. In the past I helped someone go 460BB, but now I hear you can get 420 out of an M with good heads and save some swap issues.

 

If the blower fits the 400 then it will fit the 351. There are only internal differences between the two. Externally it is the same. At one time paxton sold a bolt on kit for the 351/400 marine engines. I have seen one and it works ok for what it is.

If you are going the supercharger route for sure then the 8.3:1 compression ratio the 4v "C" heads on your 351 will give you will be a good setup. If you ran it n/a it would only give you a small bump (.3) in compression.

I naturally from my past experiences with 351/400m engines would suggest a 429/460 instead. They are cheap and not a big deal to swap. For a offroad truck like yours you would be much happier with the big block. They have good power and torque stock. If you did want more from it then the aftermarket is decent and getting better every year. I suggest getting ahold of someone with a big block equipped bronco and see what your missing out on. They do weigh more but if you are willing to spend some cash you can get rid of the iron heads, water pump and intake and you will save a bunch right there. I have always gotten the same mileage (better when towing) with the big block. Put a big block in your Bronco and you too could be a D44 u-joint breaking machine.

I have had blocks crack up multiple cylinders and have had crank oiling issues personally on my 85,000 mile 351m ( unfortunatley not a myth for me). I even bought another 351 shortblock and other performance parts to put back in the bronco but realized it was a waste buying aftermarket parts for the smallblock when the same money could be going into a big block and sold these to get the big block. Between my father and I we have not had 1 issue with any of our big block trucks/broncos. We used to rebuild the small blocks and run them but now no questions asked they get pulled right away and replaced with big blocks.

It does sound like you are already set on the 351 build. Don't let what I say discourage you. We did have a 400m that gave us alot of trouble free years. Well whatever you do, post it up in the build thread and give some before/after thoughts. Good luck.

 

so what happened with the 351m build?they are rather tough but all of this talk about myth's and you don't even know if a blower for a 400m will work on a 351m?they are physically identical other than stroke.just build the 400m if you must stay with a m series engine.had a friend that ran one in a 84 f150 rclb about 15 years ago that went 7.90's in the 1/8 on motor but it took alot of racy parts to do it.i'd scrap the smaller cube m for a 460,more reliable and parts are easier and cheaper to come by!you are also limited to a VERY small selection of aftermarket parts choices(especially the intake,unless you use the adapters and then use a 351c intake).i've seen more than a couple m motors break the crank's and the oil system is very similar to ancient indian style ditch irrigation.ohh yeah,how do you figure a 351m block is 150 pounds lighter than a 460 block,you better get some new scales.the complete engine is heavier but not a huge weight difference when comparing the blocks.

 

ok so the build is done,after much part swapping back and forth and time behind the wheel this is what i went with and for the budget i am on its the best i got...

i kept the 351m, ditched the cleaveland heads idea, and cant afford the edelbrock "M" heads so i kept the stock heads and i went with a summit camshaft kit, (duration 276/286 degrees and lift .509/.509) an edelbrock 600, a holly street dominator intake and a set of cyclone headers. for a power adder, since i am not made of money anymore, i went with a dynotune nitrous kit and went with the 150hp jets.

on the street the truck has a nice sounding mildly rough idle and is quite a bit more responsive to throttle than before. she now goes up the hill to my house in 4th gear without having to downshift and will fry the passenger tire when making hard right hand turns. being able to smoke 33's while still running the stock 355 gears is also quite nice...lol... on the straight line she will spin posi for a few seconds and chirp 3rd (4spd with a granny first) she does 0-60 in roughly 10 seconds and now tops out at about 110... (dont tell maine state police...lol...) in 4wd she does very well and has more than enough power to clean out all 4 tires. since it it has been reported these 351M's only had 176hp factory i am just guessing she is in the ballpark of 225-250hp... now for the real fun...lol...

i got the bottle filled and went wheeling and encountered some mud and since it is winter (nice warm 50 deg day) and it is maine the thawed mud was DEEP! i got stuck... dropped tire pressure to around 10lbs and it didnt help so i unwound the winch and got her out... followed the trail for a few hours got souped a few times but didnt get a real opportunity to use the nitrous... so i pulled out onto the street and decided to try it out... WOW! 10 lbs of air sure gave the old girl plenty of street traction, now i can't say i am 100% that she stood up but there are scrape marks on the road and on the bottom of the nut on the trailer ball on my reese hitch has been ground at a 45degree angle! one second im dropping the clutch and hitting the nitrous the next second i'm trying to figure out why i'm looking at the tops of trees! once the whole "what the hell just happened?!?!?" feeling wore off, i get control of the truck again and pull to the side of the road... with my heart beating like i just got chased by an angry bear and a hands shaking from the adreneline dump i just experienced, i decide its time to head home... i release the clutch and hear a loud series of bangs and the truck goes nowhere... after a brief inspection i see i have sheered off the rear u-joint... so i unbolt the driveshaft and i lock the old girl into 4wd and start heading home in my newly redesigned front wheel-drive 1980 bronco...

now i don't know what the actual hp of this truck is weather it is on the juice or not but i can tell you this, i have had some fast cars and some scary fast cars and an 8000lb bronco that stands up that easily falls into the scary catagory... this truck was fun to build and is a blast to drive, if you can get over the 6-7 MPG she gets...

here is a picture i took today of her in the snow storm we are having right now...




p.s. i was also facing up a fairly steep hill...